Agricultral Land Dispute

Sir, I would like to know about the legal dispute we have between our cousin for Agricultural Land. Situation lies like this....My Grandfather had a agricultural land which was later divided among my father & his 5 brother. Later my father purchased 2 parts from his brother(Ram & Shyam) in legal way(Having purchased documents) but which was not partitioned at that time & even in mean other Uncle purchased 2 other parts from rest of his brother (Laxman & Bharat)....now total property was totally divided between my father & uncle solely. Now one of cousin( Son of Shyam), put a case stating that his father was mentally unstable at the time of sale of property & he wants his part of property from his parent but in reality his dad was a not having any mental illness. Case is pending in court from last 4 years & our land is occupied by cousin (actual partition land will be more than what we have now with us) its aprox 30%. How we can resolve above issue? Can we go ahead for partition of land, but my cousin are not agreeing for partition in such a time, as property will be reduced from there hand? All this year they used our property for there own purpose? Whats solution do you advise for us?